Can you help make this a better article? What good localities have we missed? Can you supply pictures of better specimens than those we show here? Can you give us more and better information about the specimens from these localities? Can you supply better geological or historical information on these localities?

The arfvedsonite-series minerals belong to the sodic-amphibole sub-group and they form a solid solution series. They are common in alkali-rich igneous rocks ranging from carbonatite, nepheline-syenites towards alkali-granites. Alkaline massifs often show a gradual development of different alkaline rocks during their active period, and they often contain a large number of different amphibole species. There is not always a one to one correlation between the host rock and its pegmatites with regards to the amphibole specie(s) present. The arfvedsonite bearing Hurricane Mt pegmatites hosted in a riebeckite-granite are good examples.

Magnesioarfvedsonite is the most common arfvedsonite mineral, being abundant in silica undersaturated rocks such as carbonatites and nepheline-syenites. The largest crystals may reach sizes up to 60cm. Arfvedsonite is more typical for alkaline granites and syentites and their pegmatites. The best specimens are found in vugs in these pegmatites, with the recent finds from Malawi as a prime example. It appears that the localities producing the best arfvedsonite-series mineral specimens has a high Fe/Mg ratio, thus being arfvedsonites.

The locality producing the best specimens has historically been Mount St. Hilaire, but as collectors does not have access here today, Mt Melosa in Malawi produces the best specimens today.

There is a continuous series between the arfvedsonite minerals and the corresponding riebeckite-series minerals. There is often an hydrothermal alteration from arfvedsonite to riebeckite in the late stages of pegmatite formation. There is also a continuous series between arfvedsonite and calcic amphiboles such as the hastingsite-series minerals, often also with more excotic intermediate sodic-calcic amphiboles present.

Probably the best crystals found so far are the black prismatic ones from St-Hilaire found in pegmatite dikes that are occasionally encountered during quarry operations. They can get up to abut 20 cm but the best specimens, sharp shiny terminated single crystals are in the 10 cm range. Also “It has also been found as 1-5 mm long, dark green to gray and black prisms in marble xenoliths…Fresh, unaltered crystals are black with vitreous to dull luster. In altered pegmatites some of the crystals may be partially altered or etched. These cryrstals tend to be somewhat fibrous, deeply pitted, occasionally hollow with a dull luster.”1 It would be hard to imagine an arfvedsonite specimen from St Hilaire selling for more than $500 unless it was associated with some good crystals of one of the exotic minerals for which the locality is well known.

"Recent analytical work (yet unpublished) on MSH amphiboles confirmed the following valid species:ArfvedsoniteMagnesioarfvedsoniteFluoro-magnesioarfvedsoniteFluoro-potassic-magnesioarfvedsonitePotassic-magnesioarfvedsoniteIn addition there are at least 5 unapproved "named amphiboles" with arfvedsonite root names, which are potentially new species. Based on this recent work, arfvedsonite sensu stricto (s.s.) is actually uncommon, which is at variance with earlier, rather scant data (Horváth & Gault 1990 etc.). There is no way to visually identify any of these species and when labeling specimens one should bear this in mind. Existing labels on specimens, unless specifically analyzed, are most likely wrong. As with large groups like the Eudialyte group unanalyzed specimens should be labeled to reflect that (i.e. eudialyte group). Arfvedsonite series or arfvedsonite sunsu lato (s.l.) on the labels may be the preferrable way to go".1

There is also several other amphibole species described from the Poudrette quarry, each found in one or more of the six distinct mineral environments that has been defined here. Arfvedsonites are the dominant amphibole in the "pegmatite" and "altered pegmatite" environment and also occurs in the "marble xonoliths".

Crystals up to 23 cm are reported in Dana’s Text, 4th edition. “Weighing down the front of the stand were three dull black prisms of Ilimaussaq arfvedsonite which looked like burnt campfire logs, the biggest one 20 cm long.”1 The St-Hilaire material comes from an active quarry and most specimens found there are found in fresh pockets in unweathered rock. The Greenland material was probably found near the surface and subjected to some weathering. Most of the collecting in Greenland is done by scratching around on the surface and at best the surface rock is loosened with a little explosive. I would love to see what some of those places would produce if an active quarry were working the locality. The Ilimaussaq complex is considered a potential resource base for REE, and commercial mining is continuously evaluated. If a mining operation will start, it will probably be a large scale modern mining operation, and it is unlikely that any mineral specimens will be saved from the crushers.

The Ilimaussaq intrusion is the youngest of a number of syenitic bodies in the late Precambrian Gardarprovince of South Greenland. It contains a complez mix of various alkaline rocks with quite complex mineralogy. Sørensen(2001) gives a good overview of the geology of the area.

Arfvedsonite is the dominant amphibole in all the Ilimaussaq rocks. The arfvedsonite has a very low Mg content (Mg<<1%) and a relatively high K content, somtimes more than 0,5 apfu, thus being a potassicarfvedsonite. Pekov et al. (2004) gives a detailed and typical description on how (potassic)arfvedsonite occurs here:

"The locality of the holotype material is the “Pegmatite Valley”; the small stream in the valley being the lowermost tributary to the Lilleelv river in the Kangerluarsuk area, Southern part of Ilímaussaq complex, altitude about 260 m. Potassicarfvedsonite occurs in one or more pegmatite veinlets more than 20m long, and up to 0.5m thick, crosscutting naujaite, on both sides of the stream in the Pegmatite Valley. The pegmatite veinlets mainly consist of white coarse-grained analcime with subordinate amounts of fine-grained sodalite, microcline, aegirine, crude crystals of steenstrupine-(Ce), eudialyte,and epistolite. Potassicarfvedsonite forms well shaped prismatic crystals from a few cm up to 15 × 0.8 cm, showing the {110} and {010} forms, included in an analcime matrix. In other parts of the veinlets, preferably the marginal parts, it occurs as mosaic individuals up to several cm in size,which combine to massive, sometimes divergent and curved, aggregates, constituting up to 30–50% of the pegmatitic rock."

H. Sørensen(2001): Brief introduction to the geology of the Ilímaussaq alkaline complex, South Greenland, and its exploration history, The Ilímaussaq alkaline complex,South Greenland: status of mineralogical research with new results, Geology of Greenland Geology of Greenland Survey Bulletin 190.

The early Cretaceous Chilwa Alkaline Province has an exceptional range of lithologies from carbonatite to granite. It lies at the southern end of the East African rift and is unique for it’s essential intrusive character. The largest and most recent (ca 113Ma) intrusions are those that consist of syenite and peralkaline granite. The Chinduzi-Chikala (nepheline) syenites are older (up to 130Ma)

The well crystalized minerals from the area comes from the Zomba-Malosa intrusion and the Chinduzi-Chikala mountain range. Mount Zomba consists of a central plug of syenite, an inner ring of quartz microsyenite and an outer ring of peralkaline granite. Mount Malosa the consist of a heterogenous mix of quartz-syenites and granites. These two mountains are divided by a deep rift valley. Numerous amphiboles has been identified from the Zomba-Malosa intrusion, and the “amphiboles cover an exceptionally extensive range of species including calcic, sodic-calcic and alkali types. They define distinct Zomba and Malosa trends of Mg depletion and alkali enrichment and increase in Fe3+: Fe2 ratios”(Wolley and Jones, 1992).

The Chinduzi-Chikala mountain range consist predominantly of of syenite, which gradually becomes more silica undersaturated from east(syenite) to west (nepheline syenite)

The attractive mineral specimens originates from pegmatites related to these rocks, and two important types of pegmatites are present in the area:. “ In the Chinduzi-Chikala range of mountains, nepheline-syenite pegmatites occur. These contain large well developed aegirine crystals “….. up to 5 by 2.5 cm in size…..” as reported by Bloomfield (1965). In contrast, granitic pegmatites are found in the Zomba Mountain and Malosa Mountain. The northwestern fault scarp in particular has an abundance of these pegmatites and it is from these deposits that the best specimens have been collected. To the south, the Zomba section of the complex has far fewer pegmatites.” Cairncross(2004).

Mineral specimens are retrieved from the northwestern part of the Malosa mountain where a series of major faults cut through the mountain. These have produced scarps with vertical cliff faces up to 800 meters high. The Pegmatites that contain the minerals strike across the mountain and down the vertical cliffs so that some can only be reached by climbing down the cliff faces. Because the Quartz-rich Pegmatites are more resistant to weathering, they form narrow ridges that the collector can balance and walk along.

The pegmatites at Mt. Malosa produce probably the best arfvedsonite crystals on the market today ( 2012), but they still play a second fiddle to the spectacular aegirine specimens that are found here. However “Arfvedsonite forms very well-developed crystals, most of which are between 1.5 and 3 cm, though perfect crystals as large as 30 cm have been found. The generally sharp prismatic crystals all show the prism {110}, which is often strongly striated. In addition to the prism, most of the crystals show the pinacoid {001} and the prism {111}. The crystals are black and generally not as lustrous as the aegirine crystals. Many crystals show incipient to advanced alteration to asbestiform riebeckite.”

I have not found published any analysis of the arfvedsonite from Mt. Malosa, as all references points towards Petersen et.al (1994). The identification of the amphibole as arfvedsonite is however consistent with a general trend of alkali and Fe enrichment in the Mt Malosa syenites.

Large (up to 18x8x3.5 cm) arfvedsonite crystals have been found in the quartz core of alkali granite pegmatites on the Northern slope of Mount Ulyn Khuren. The crystals are often twinned. The pegmatites belong to the Khaldzan Buragtag alkaline massif. The arfvedsonite os K-rich and has a very low Mg content.

Arfvedsonite is found in an alkali pegmatite with feldspar, quartz, zirkon and probably other minerals hosted in a nepheline syenite. There has not yet been published any petrological papers on these rocks, but Tomasz Praszkier of Spirifer Minerals give the following description of the locality:

"Geology of this locality is typical for the area – pegmatite vein is going though nepheline syenites. Thickness of the vein varies from few tens of centimeters to over a meter. Vein is built mainly by feldspar and arfvedsonite. Pockets are very small and usually crystals are only partly free growing. Also the vein is mined in superficial part so it is very weathered and many crystals fall apart. The biggest known arfvedsonite crystals of good quality reach over 12 cm! Frequently on the termination and sometime at the prism faces there is second generation of arfvedsonite formed as hairy-like crystals. Beside of arfvedsonite, feldspar (orthoclase) is frequent in the pockets. Less common are quartz (crystals reaching up to 15 cm), orange zircons (up to a few millimeters) and blade-shaped epidote green crystals. Some pockets contain also octahedral magnetite crystals reaching up to 1 cm"

EDS data kindly provided by Jordi Fabre indicates arfvedsonite for both the green and black variety, as they show neglectable amounts of Al, Mg and Ca are neglectable and Si, Fe and Na as the dominant elements.

The Lovozero Massif is one of the largest alkaline complexes in the world. It shows a wide variety of alkaline rocks and a large number of amphiboles can be found here. (Magnesio)arfvedsonite is common in many of these rocks. In the Severenyi quarry, (magnasio)arfvedsonite can be found in crystals up to 15cm embedded in microcline in pegmatites. It occurs with microcline, orthoclase, aegirin and more exotic minerals.

Arfvedsonite FluoroarfvedsoniteUnited States New Hampshire, Carroll County, Conway, North Conway, Hurricane Mt. localities

Arfvedsonite 7,8cm specimen

Arfvedsonite 9mm FOV

Arfvedsonite 7,8cm specimen

Arfvedsonite 9mm FOV

Arfvedsonite 7,8cm specimen

Arfvedsonite 9mm FOV

Arfvedsonite 11,5 cm crystal

Arfvedsonite 11,3 cm specimen

Arfvedsonite 11,5 cm crystal

Arfvedsonite 11,3 cm specimen

Arfvedsonite 11,5 cm crystal

Arfvedsonite 11,3 cm specimen

Arfvedsonite 2 cm FOV

Arfvedsonite 2 cm

Arfvedsonite 2 cm FOV

Arfvedsonite 2 cm

Arfvedsonite 2 cm FOV

Arfvedsonite 2 cm

This is an important locality for the species. Although the occurrence of arfvedsonite is not uncommon, well terminated specimens are quite rare. Arfvedsonite is found here in miarolitic cavities and embedded in the pegmatites of the Conway Granite.1 A range of morphologies are exhibited. Generally the crystals are either terminated well at one end and then taper to a more indistinct termination at the other end or both terminations may be indistinct. Doubly terminated prisms have also been observed. Those that occur in the cavities either display a single well formed termination and taper in width away from the cavity into the pegmatite or if entirely within the cavity they are generally contact terminated, prismatic, equant (not tapered) and quite lustrous. This tapering of Arfvedsonite is found at pocket locations, throughout the pegmatite body and at contacts with the country rock demonstrating cooling rates and nucleation times within the pegmatitic body. The tapered end had less time to grow as the pegmatitic body cools. The wider end and typically the more distinctly terminated end has had longer to nucleate. Arfvedsonite that occurs outside of cavities, embedded in pegmatite demonstrates this tapering as well. Generally, arfvedsonite crystals from here are black, vitreous, opaque, striated, and prismatic. Most crystals observed ranged in size from 1cm to 5cm long, although longer prisms have been observed. The largest crystal of Arfvedsonite observed measured approximately 11.5 x 4.0 x 3.5 cm. Associated species include quartz (both smoky quartz and rutilated quartz) some being reverse sceptred, microcline, albite (var: cleavelandite), astrophyllite, riebeckite (var: crocidolite) and zircon.2

The host rock of the pegmatites are a riebeckite granite, but the amphibole in the pegmatites is arfvedsonite. The primary arfvedsonite contains F and Li, wich gets gradually lower towards and in the miarolic cavities. For some crystals, the F/OH ratio is>1 and the amphibole will consequently be a fluorarfvedsonite. The "crocidolite", i.e a fibrous late hydrothermal amphibole sometimes found in the miarolic cavities is a riebeckite.7

Sharp, well formed shiny crystals both equant and prismatic habit up to about 1 cm.1 A better description comes via an email from Bart Cannon, who lives in Seattle, Washington. “The largest xls were about 3.5 inches. They occur in miarolitic cavities in the agpaitic phase of the Golden Horn Granite associated with smoky quartz, astrophyllite, zircon, and zektzerite.”

Stull (1973) supports Bart Cannon's size designation, as he describes crystals to 2-3 in found in miarolic cavities in the alkali granite in the Golden Horn Batholith. Stull also provides analytical data on the amphiboles from both the biotite granites and the alkali granite. He found some differences both in chemistry and optical properties between the amphibole in the granite itself and in the cavities, but all the analysed samples fall within today's range for arfvedsonite.

http://www.mindat.org/photo-71470.html On the locality are known complete, terminated arfvedsonite crystals up to 18x8x3.5 cm (displayed in the old Museum of MGRI in Moscow). Twinned xls are more abundant than monocrystals in quartz core of the pegmatite.

This is my first attempt at helping with "best minerals". I would appreciate your guidence and feedback on this post.Hopefully, I'm on the right track. Sending information for 2 localities, 3 of 6 images, 3 to follow. So, here goes.

Two New Hampshire Localites:

Arfvedsonite United States New Hampshire, Carroll County, Conway, Hurricane Mt. localities

This is an important locality for the species. Although the occurrence of arfvedsonite is not uncommon, well terminated specimens are quite rare. Arfvedsonite is found here in miarolitic cavities and embedded in the pegmatites of the Conway Granite.1 A range of morphologies are exhibited. Generally the crystals are either terminated well at one end and then taper to a more indistinct termination at the other end or both terminations may be indistinct. Doubly terminated prisms have also been observed. Those that occur in the cavities either display a single well formed termination and taper in width away from the cavity into the pegmatite or if entirely within the cavity they are generally contact terminated, prismatic, equant (not tapered) and quite lustrous. This tapering of Arfvedsonite is found at pocket locations, throughout the pegmatite body and at contacts with the country rock demonstrating cooling rates and nucleation times within the pegmatitic body. The tapered end had less time to grow as the pegmatitic body cools. The wider end and typically the more distinctly terminated end has had longer to nucleate. Arfvedsonite that occurs outside of cavities, embedded in pegmatite demonstrates this tapering as well. Generally, arfvedsonite crystals from here are black, vitreous, opaque, striated, and prismatic. The crystals observed ranged in size from 1cm to 5cm, although longer prisms have been observed. The largest crystals of Arfvedsonite observed were about 5.0 cm long with one specimen being over 2.0 cm wide. Associated species include quartz (both smoky quartz and rutilated quartz) some being reverse sceptred, microcline, albite (var: cleavelandite), astrophyllite, riebeckite (var: crocidolite) and zircon.2

Arfvedsonite United States New Hampshire, Carroll County, near Moultonboro, at Red Hill

The first mention of “hornblende” at Red Hill seems to have come from George W. Hawes, 1878. He describes the finding of “fine to superb crystals” in Moultonborough.3 Arfvedsonite is referenced by Januzzi & Seaman, 1976. They write, “Arfvedsonite occurs in nepheline-syenite, certain porphyries and in granite pegmatites. Noted in pegmatites at Red Hill near Moultonborough, Carroll County, New Hampshire…”.4 Hawes’ description is mentioned again by Meyers & Stewart, 1956.5 Subsequent papers have been written discussing the petrology and mineral assemblages of the Red Hill Complex.6 Specimens from this location seem extremely limited and unavailable to observe or characterize. Nonetheless, the occurrence is believed to be valid.

Rock,I have visited the Greenland localities (Ilimaussaq-complex and Narssarsuk) many times and have a number of Arfvedsonite specimens from there. Some of the arfvedsonites from Ilimaussaq are the K-analoge - "Potassicarfvedsonite". Even if the Arfvedsonites from Ilimaussaq occur in weathered outcrops, very sharp crystals are also known when enclosed in zeolites (analcime).Arfvedsonite are also known from the syenitic rocks of the Oslo region sometimes occuring in crystals to e few cm in miarolitic cavities and pegmatites. Following the new and complex nomenclature for amphiboles, the exact identitity of amphiboles from the different localities in the Oslo-region are not allways known (which maybe the case also for other localities for "arfvedsonite").Knut

Knut. Thats good information. I think the new nomenclature for several minerals like micas etc make it difficult to know just what they are from old and well established localities. Its quite a problem not easy to fix. Thats why I dread trying to work on minerals like Arfedsonite or some of the mica minerals. What percentage of these minerals do you think are correctly named in the mindat galleries? 20%?

Olav, Not only do I hope you build on them, but you should feel free to take them over entirely. At the end of all the articles should be the date year and month of your update. I am revamping David Von Bargans best minerals Fluorite USA and have had to split it into two separate articles because of the size. I am putting the date at the bottom of the article and the top of the date of his first edition and my name with the date of the second edition. This will be important in the future, especially for "big minerals" so we can know the last date that all the uploaded or recently uploaded images of that mineral were scanned for possible inclusion in the article. We will always be doing minor modifications and additions to the articles, but the next time a guy comes along to do a major update of the article he can again look at all the images, but will also know the last time the images for that mineral were looked at and at that point he can look only for images that have been uploaded for that particular mineral.

Did you pick up on that cool new tool that David made for us that automatically reverses the locality strings? Go to that locality, click on the edit menu, and the string reversal tool is the last menu choice in the edit menu.

Thank you for writing the text for the New Hampshire localities, it is exacly that kind of information I guess most of us would like to know about a locality. Thanks again. I could not find any of the photo's you have attached to your messages here in the database. I would appreciate if you could upload images 100_8168a and 100_8190 to the database, so that they can be used in the article. Do you know if any of the references you list contain any analysis of the arfvedsonite? Quite often, the alkaliamphibole in silica-rich pegmatites are intermediate between riebeckite and arfvedsonite, and more often closer riebeckite than arfvedsonite according to Howie's book "Rock forming minerals" on amphiboles.

Ronald,I must agree with Wayne, you have collected some very nice Afrvedsonite from Hurricane Mt. Having collected off and on for the past 20 years at Hurricane Mt I truly appreciate these specimens. I hope every one on Mindat appreciates just how difficult these are to collect, they are brittle and shatter very easy. Olav - Reibecikte is also found at Hurricane Mt. Has anyone posted a picture under short was light of a matrix specimen form Hurricane Mt. The feldspar fluoresces a deep red and the zircons are a deep yellow. So I am sitting here looking at Hurricane Mt out my back picture window and it is calling me so I guess I need to take a hike real soon .

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